Notes on the Tobago Glassfrog, Hyalinobatrachium orientale
Two recent papers document male parental care in the Tobago glassfrog population. Murphy et al (2012) reported males attending nests while calling, presumably to attract more females to deposit more eggs. This past month we observed males attending up to three nests. Lehtinen and Georgiadis (2012) report males attending up to six egg masses. The eggs masses and calling males are frequently on the underside of leaves that overhang the water (see above). Our observations in the past month suggegst that glassfrogs are frequently using Heliconia leaves that overhang the water and that nests may be 1-4 meters above the water (see photo). In 2011, Murphy et al. observed small crabs on the same plants used by the frogs. Placing eggs on the underside of leaves may be a response to crab predation, since the crabs are unable to walk on the underside of leaves. However, the purpose of male attendance remains uncertain. Males covering egg masses may act to prevent dessication, but a male with six nests may find protecting all nests from drying quite difficult. Another possibility is that the male is transferring some molecule(s) to the eggs that are antifungal or antibacterial. The presence of the male may also prevent predation or parasite infection from insects. Twelve eggs masses examined by Lehtinen and Georgiadis (2012) had 21-36 eggs (mean = 28.3). And, they found tadpoles capable of prpeling themselves up to 40 cm (or 36 times their body length). The distribution of these frogs on Tobago also seems to be more widespread than previously thought because we heard them calling from numerous stereams that drain the island's Main Ridge in all direstions.